Formation of lactoferrin/sodium caseinate complexes and their adsorption behaviour at the air/water interface

•Heat stability of lactoferrin can be improved in the presence of sodium caseinate.•Sodium caseinate molecules prefer to attach to the surface of lactoferrin molecules.•The formed sodium caseinate-lactoferrin complexes have a core-shell structure.•Complexes formed at different ratios have different structure and functionalities.

This research investigated the complexation behaviour between lactoferrin (Lf) and sodium caseinate (NaCas) before and after heat treatment. The results showed that heating facilitated their interaction and different complexes were formed at different Lf/NaCas ratios. The presence of low concentrations of NaCas resulted in the rapid precipitation of Lf, while no precipitation was observed at the NaCas concentrations higher than Lf/NaCas ratio of 2:1. The formed complexes at the ratio of 2:1 have an average diameter of 194 ± 9.0 nm and they exhibited a great capacity in lowering the air/water interfacial tension. Further increase of NaCas concentration to ratios of 1:1 and 1:2 resulted in the formation of smaller complexes with average diameters of 60 ± 2.5 nm. The complexes formed at these two ratios showed similar adsorption behaviour at the air/water interface and they exhibited lower capacity in decreasing the interfacial tension than the ratio of 2:1.